1. Field of the Invention
This invention relates to a process wherein an aqueous solution comprising boron ions in solution is treated with a water soluble polymeric chelant to coordinate with the boron ions. Water and low molecule-weight materials are separated from the boron-containing polymeric chelate by separation means such as dialysis or ultra-filtration. The chelate is then subjected to acid treatment which removes the boron-containing ion, and the chelate and ion are separated. The polymeric chelant is then recycled and reused.
2. Description of the Art
In Soviet Union Pat. No. 1122644 (dated Nov. 7, 1984), M. I. Yakushkin et al. disclose that N-beta-hydroxyethyl glucamine is used as a starting material for the synthesis of a boron-selective sorbent. The glucamine is added to the chloromethylated cross-linked copolymer of styrene and divinylbenzene to form a water-insoluble polymer. This reference does not teach the use of a water-soluble polymer.
J. Nomura et al. in Great Britain Pat. No. 2,135,983 disclose the separation of borate ions from water at pH of 5-11 by contacting the aqueous borate-containing solution with an absorbent comprising hydroxides or hydrated oxides of rare earth elements and preferably contacting the absorbent containing the absorbed borate ions with a desorption solution of pH of 2 to 4 or pH 12 to 14 to desorb the borate ions and regenerate the absorbant.
N. B. Galitskaya in Soviet Union Pat. No. 785,321 discloses a boron-selective sorbent by the amination of halogenated cross-linked vinyl copolymer with tris-hydroxymethyl amino-methane.
A solid-phase cation-exchange resin for the removal of unwanted ions is brine, including borate, is described by J. M. Lee et al. in U.S. Pat. No. 4,415,678 and No. 4,405,576.
M Kurihara et al. disclose on European Pat. No. 44872 a technique for selectively separating water-soluble materials such as borate from aqueous solutions using reverse osmosis membrane having a porous, support-carrying barrier layer of cross-linked isocyanurate polymer.
In U.S. Pat. No. 2,813,838, W. R. Lyman et al. disclose a boron-absorbing resin and a process for removing boron compounds from liquids. R. Kunin et al. disclose in I & EC Product Research & Development, Vol. 3, p. 305 (1964), a characterization of a boron-specific ion exchange resin. C. L. Mehltretter et al. describe boron-selective ion exchange resins containing D-glucitylamino radicals in I & EC Product Research & Development, Vol. 6, p. 145 (1967). E. M. Chemtoh in U.S. Pat. No. 3,567,369 disclose an ion exchange resin for removing borates from brine. All of these processes are concerned with an ion-exchange resin which is insoluble in water.
It is known by a number of techniques to treat an aqueous solution with a water-insoluble ion exchange resin. However, the problems associated with this approach include a kinetic performance that is fairly slow and a complicated process to prepare the water-insoluble polymer. It is therefore very desirable to have a process where the organic chelant is water-soluble to react quickly with the boron ion in one phase, and remains in solution during separation using dialysis or the like. Further, the polymeric chelant is recyclable and may be reused again and again.